Effect of Ru on γ/γ' microstructural evolutions and precipitation of TCP phases during thermal exposure at 1100 °C in a single crystal superalloy

Abstract

The effect of 2 wt% Ru on γ/γ' microstructural evolutions and precipitation of TCP phases were investigated in two experimental alloys. The two alloys were subjected to unstressed thermal exposure at temperatures of 1100 °C for periods of 100, 500 and 1000 h. The microstructures of the samples before and after thermal exposures were characterized. Directional coarsening of γ' phases and the precipitation of TCP phases were observed in the both alloys after long-term exposure. The experimental results show that Ru has a very significant effect on the suppression of TCP phases by influences the partitioning of elements. Detailed analysis showed that Ru increases the lattice misfit strain, resulting in more dense and stable interfacial dislocation networks, which can promote the stability of γ/γ' microstructures by delaying topological inversion. Ledges and grooves at γ/γ' interfaces associated with the dislocations and strong segregations of Cr, Co and Re along the dislocation networks were both observed, under which a detailed explanation of the coarsening process during thermal exposure was given. • Ru increases the microstructural stability. • Ru increases the density and stability of dislocation networks. • Ru promotes the stability of γ/γ' microstructures by delaying topological inversion. • Ru reduces the nucleation of TCP precipitates.